Inkjet printing mechanisms use cartridges, often called "pens," which shoot drops of liquid colorant, referred to generally herein as "ink," onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image on paper media, for instance, the printhead is propelled back and forth across the page, shooting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett-Packard Company. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).
To clean and protect the printhead, typically a "service station" mechanism is mounted within the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which hermetically seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as "spitting," with the waste ink being collected in a "spittoon" reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead.
Over the last decade or so, hardcopy printing has rapidly become an affordable technology in our every day life for outputting various different types of computer-generated information. The most common print media is paper, although other media are often used, such as transparencies, foil, and fabric, to name a few. For instance, paper media is printed upon and used as a reminder for information.
Despite the advances in electronic information display technology, the use of paper as a hardcopy print media has shown no signs of decline. Indeed, the trend has been toward improving the print media to improve the print quality of the final image, as well as researching new types of hardcopy print media, such as photo-quality paper and printable fabric. Still, thus far, the hardcopy printing technology has focused on providing a permanent print output, while neglecting situations where a reusable printing technology may be preferred. For example, it may be desirable to print a hardcopy output of various reoccurring information, such as printing the current day's news or the daily stock prices from a computer website location. Other situations where reusable media may be preferred are as simple as an electronic mail message from a friend that one would like to share with family, or simply a draft of an article or report that one would like to proofread. It is apparent that there are many different situations where it would be helpful to have hardcopy in hand to read, but a permanent copy of the information is simply not required.
Thus, from both an economical and an environmental point of view, it would be desirable in this information age to have a system for temporarily recording information on a familiar hardcopy output, without later throwing the hardcopy away, wasting both ink and the media, which is typically paper. Granted, paper is recycled today in many homes and offices to lessen the waste of disposing the hardcopy output. Unfortunately, recycling paper has several economic and environmental side effects, such as the additional air pollution caused by vehicles hauling the waste media to the recycling center, as well as the consumption of fossil fuels used to power these vehicles. Furthermore, additional energy, often in the form of electrical energy, is required to process the waste paper at the recycling plant. Thus, it would be desirable to have a reusable media that avoids wasting media and conventional recycling.
One approach recently advertised by the E.I. DuPont de Nemours and Company of Willmington, Del., is an electronic journal display. Here, the user must connect a cable between the computer output and the journal display device. After making this connection, the computer then downloads the information into the journal display device where the information is stored for later reading at a remote site. This journal display device may be useful for reading newspapers and other periodicals, but unfortunately, it is cumbersome to use, requiring the repeated coupling and uncoupling of the cable each time new material is downloaded. Furthermore, a totally separate piece of equipment is required beyond that found in the normal office environment. Thus, it would be desirable to provide a printing mechanism, such as an inkjet printer, which is capable of printing both a permanent record on a single-use or "permanent" print media such as paper, and a temporary image on a reusable print media.